[TESTIS SPARING SURGERY FOR ADULT MATURE TERATOMA OF THE TESTIS; REPORT OF A CASE].

A 25-year-old man presented complaining of a painful, left scrotal swelling. He first noticed a mass in his left scrotum during childhood, but, in the absence of clinical symptoms, did not seek medical attention. We detected a left testicular tumor which was elastic, firm and smooth. Serum levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and lactate dehydrogenase (LDH) were all within normal range. Magnetic resonance imaging (MRI) and ultrasound revealed a solid tumor with cysts accompanied by intracystic hemorrhage and calcified walls. From the above findings, the tumor was suspected to be benign and, we therefore planned testis-sparing surgery. We performed tumor enucleation under cold ischemia. Since an intraoperative frozen section revealed the tumor to be benign, we preserved the remaining testis as planned. The final pathologic diagnosis was a mature teratoma without a malignant germ cell component. Evidence of recurrence has not been observed five years after the operation. In conclusion, when a mature teratoma that has been present since prepuberty is suspected in an adult, testis-sparing surgery should be considered.